A typical milling machine is an apparatus that features a rotating milling cutter having a number of indexable cutting inserts, where the rotating milling cutter is passed over the workpiece to remove material from the workpiece. Once a cutting edge of an indexable cutting insert is dulled, the insert is removed and rotated or "indexed" to expose a sharp cutting surface.
The use of milling cutters having replaceable cutting tool inserts began as long ago as 1917, when Fred P. Lovejoy invented the use of replaceable blades in order to obtain the economic advantages of having to replace only the dull portion of the tool, not the entire tool itself. Since that time, a myriad of cutting tool inserts having different shapes and sizes have been developed. However, few improvements have been made in the way cutting tool inserts are indexed and secured in milling cutters.
Over the years, several basic approaches to indexing and securing cutting tool inserts have been developed. One method, and current industry standard, involves securing a cutting tool insert to the milling cutter with a screw that passes through the insert and is tightened into a threaded hole in the cutter. This method has some mechanical advantages as the size tolerances between the screw and screw hole in the insert may be small enough to provide a relatively stable mounting system. However, the industry standard systems are not without disadvantages. In order to index an insert using the industry standard insert and cutter, the screw holding the insert in place must be completely removed and subsequently replaced after the insert has been indexed. The complete removal of a screw presents challenges as a typical operator is forced to grasp the cutter with one hand while simultaneously removing the screw and controlling the insert with the other. Should the operator drop the screw, it is likely to become intermingled with chips and other debris and be difficult to find. Similarly, if the operator drops an insert, there is a chance that a sharpened surface will be chipped or dulled resulting in the insert being unusable. In addition to the practical challenges of removing and installing industry standard inserts, the presence of a hole in the middle of the insert reduces the strength of the insert and leaves it susceptible to failure in situations where too much material is cut or where the milling machine is fed too quickly.
A number of top-clamping insert holders have been developed to overcome the indexing and strength problems associated with industry standard thru-hole cutting inserts. One top-clamping method uses a screw mounted adjacent to the insert and a rotatable finger clamp which contacts the top of the insert and clamps it into place. Another method uses a wedge to clamp the cutting tool insert into the milling cutter, though this method is limited as the size of the wedges required limits its use to large milling cutters. These methods eliminate the need for a hole through the insert, increasing insert strength and allowing inserts to be indexed quickly. However, they are not without their limitations. Both the "screw-mount" and "wedge-lock" top-clamping systems hold the insert in only one direction and, under operating conditions, inserts clamped in this fashion have a tendency to move unacceptably in both the radial and axial directions. In addition, the wedge-lock system may only be used with cutting tool inserts having flat top surfaces and thus is not adapted for use with rhomboid shaped cutting inserts. Therefore, a combined solution has been developed which provides a top clamp, similar to the screw-mount top clamp described above, and a cam pin which is inserted through a hole in an industry standard insert to provide axial stability. This solution allows inserts to be indexed relatively quickly, but suffers from the strength problems associated with all thru-hole style inserts.
A milling cutter which can top clamp a rhomboid-shaped insert in a fixed and stable position during operation without the use of a thru-hole lock screw, and which allows quick and easy indexing is not known in the art.